Ten fascinating natural phenomena

Aurora Borealis: Undoubtedly one of the most beautiful natural phenomena, Auroras, also known as northern and southern lights, are natural light displays in the sky, usually observed at night, particularly in the Polar regions. The phenomenon occurs when the sun gives off high-energy charged particles that travel out into space.

Penitentes
Penitentes are huge ice spikes, so named due to their resemblance to hooded monks, and can be found on mountain glaciers. The spikes can reach up to 5m in height and are a caused by the sun's rays penetrating certain parts of the ice deeper than others, causing peaks in between the dimples.

Sailing Stones
The mysterious moving stones of the Death Valley desert have been baffling scientists for decades. Rocks weighing several hundred pounds have been known to move hundreds of yards at a time, causing eerie track marks in the sand. Scientists still argue over the cause of the movement, as an initial high-wind theory appears to be ruled out by the speeds needed to move some of the larger stones and the fact some of the tracks are non-linear.

Supercells
Supercell is the name given to a continuously rotating updraft deep within a thunderstorm. These terrifying looking winds are usually formed by two storms moving in different directions and, although they can occur anywhere in the world, are usually found in the US Midwest.

Fire Devils
These sinister looking tunnels of fire, also known as fire whirls, are a rare phenomenon caused by very rapid changes to air temperature and current. Although they look like flaming tornadoes, the vertical columns usually last just a few minutes. However, with some standing at over 200ft tall and 10ft wide, the damage done in those few minutes can be immense.

Ice Circles
Ice circles are usually only found in extremely cold climates and are caused when surface ice forms around the centre of a body of water rather than the edge. A slow moving current then rotates around the ice formation creating a frozen disc within the water. Some ice circles have been known to reach 500ft in diameter and often emerge in clusters.

Gravity Waves
Gravity waves are caused by air displaced within a vertical plain, usually the result of updrafts coming off a mountain during a thunderstorm. The spirally patterns in the sky are created the updraft air is forced into a stable air pocket, causing changes in the atmosphere and altering fluid dynamics.

Algal Blooms
Not all algal blooms are spectacular, in fact the green algae covering your local pond is probably a good example of how a typical algal bloom looks. However, when the bloom occurs at sea and includes a level of phytoplankton that is often harmful, the water takes on a hue ranging that ranges in colour from light orange to terrifying blood red.

Fire Rainbows
Fire rainbows - also known as circumhorizontal arcs - appear when the sun is higher than 58 degrees in the sky and its rays pass through diaphanous high-altitude cirrus clouds made up of hexagonal plate crystals. Sunlight entering the crystals vertical side and leaving its bottom side is then refracted, causing bursts of rainbow-coloured rays to flit across the sky.

Taos Hums
Due to the fact they were first recorded in the New Mexico town of the same name, most strange rumbling noises heard without any identifiable source are referred to as Taos hums. The 'hums' are actually more commonly found in Europe and have been likened to the sound of a idling diesel engine. Listen to a clip of the sound here: http://ind.pn/aOxGTY.

From tornadoes made of fire to the sailing stones of Death Valley, our photo essay casts light on the bizarre and often terrifying side of nature